1. Technical Field
The present invention relates to epitaxial reactors and, more particularly, to a gas collector for epitaxial reactors.
2. Description of the Related Art
Continuing advances in the microchip industry have resulted the development of highly complex thin-film deposition processes for fabricating semiconductor devices that are packaged for use in the manufacture of sophisticated electronic devices. Thin films of material that are deposited on semiconductor wafers are often referred to as epitaxial layers. High speed electronic transistors, quantum-well diode lasers, light-emitting diodes, photodetectors, and optical modulators incorporate structures composed of numerous epitaxial layers ranging in thickness from several microns to as thin as a few tenths of a nanometer. These epitaxial layers are typically deposited, or grown, on a single-crystal substrate, i.e., the semiconductor wafer.
One method of forming epitaxial layers on a semiconductor wafer is known as chemical vapor deposition (CVD). In a typical manufacturing process of a wafer, for example, silicon in extremely pure crystalline form is overlayed sequentially with numerous layers of materials which function as conductors, semiconductors, or insulators. Each subsequent layer is ordered and patterned such that the sequence of layers forms a complex array of electronic circuitry. The semiconductor wafer is subsequently cut along predetermined scribe lines into individual devices, commonly referred to as "chips." These chips ultimately function as key components in electronic devices ranging from simple toys to complex supercomputers.
CVD processes normally take place within a device such as, for example, a radial flow reactor, that includes a reaction chamber. The semiconductor wafer is initially placed within a reaction chamber, which typically contains an inert atmosphere. The temperature within the reaction chamber is elevated and chemical vapors containing the compound or element to be deposited are introduced to react with the surface of the semiconductor wafer. This process results in deposition of the required film. The chemical vapors are continually introduced and removed from the reaction chamber until a requisite film thickness has been achieved.
Reaction chambers are typically constructed from a perforated section of sheet metal that is cut and folded into a segmented conduit of polygonal configuration. The segments are closely aligned so as to form a semi-continuous loop. The reactor chamber lid is pressed against the top of the conduit formed by the sheet metal in order to provide a seal between the conduit and the reactor chamber lid. Inlets and outlets are provided for the chemical vapors along inner and outer circumference of the conduit, respectively.
One problem associated with such reaction chambers is that the semi-continuous nature of the conduit does not always form a gas, or hermetic, seal the reactor chamber lid. Accordingly, chemical vapors are allowed to escape from the conduit to other parts of the reaction chamber prior to being channeled to the exhaust pipes. Another problem with such reaction chambers is the potential for contamination resulting from repeated flexing of the sheet metal over repeated openings of the reactor chamber lid. More particularly, each time the reactor chamber is opened, the conduit flexes along the same perforations and bending points. Over time, metal particulates will flake off the sheet metal and contaminate the inert atmosphere of the reaction chamber.
There exists a need for a gas collector capable of preventing the escape of chemical vapors removed from an epitaxial reactor. There also exists a need for a gas collector that minimizes the level of contamination into the epitaxial reactor.